Looking to attempt a few band practices here at home. I am already in pretty good shape due to having an isolated location, it's not like I have a neighbor on the other side of the wall. But, just to minimize the bass and drums from carrying outside I am thinking about just covering some of the windows. Unfortunately, 2" closed cell foam is very expensive, one of my windows is quite large. So I was looking at Lowes/Home Depot stuff and about the most workable cheap stuff I could see is rigid foam insulation. I am wondering whether a wood frame, with two layers of rigid insulation and a small gap in-between the layers, to put in front of the wondow would do any good at helping to deaden the exterior noise. I don't know what the sound properties of that stuff is but it's basically styrofoam. Or if anyone has a better suggestion for inexpensive material I'm all ears. Thanks!